Route Scroll events through a cc::InputHandler

ui/compositor/overscroll/ui_input_handler.h

Index: ui/compositor/overscroll/ui_input_handler.h
diff --git a/ui/compositor/overscroll/ui_input_handler.h b/ui/compositor/overscroll/ui_input_handler.h
new file mode 100644
index 0000000000000000000000000000000000000000..5424f50c19836ab94a9d9cfd1760710c3b5dc087
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+++ b/ui/compositor/overscroll/ui_input_handler.h
@@ -0,0 +1,51 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_COMPOSITOR_OVERSCROLL_UI_INPUT_HANLDER_H_
+#define UI_COMPOSITOR_OVERSCROLL_UI_INPUT_HANLDER_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "cc/input/input_handler.h"
+
+namespace ui {
+
+class ScrollEvent;
+
+// Class to feed UI-thread scroll events to a cc::InputHandler. Inspired by
+// ui::InputHandlerProxy but greatly simplified.
+class UIInputHandler : public cc::InputHandlerClient {
+ public:
+  explicit UIInputHandler(const base::WeakPtr<cc::InputHandler>& input_handler);
+  ~UIInputHandler() override;
+
+  // Ask the InputHandler to scroll |element| according to |scroll|.
+  void HandleScrollUpdate(const ScrollEvent& scroll, cc::ElementId element);
+
+  // Informs the InputHandler of the end of the event stream.
+  void HandleScrollEnd(const ScrollEvent& scroll);
+
+  // cc::InputHandlerClient implementation.
+  void WillShutdown() override;
+  void Animate(base::TimeTicks time) override;
+  void MainThreadHasStoppedFlinging() override;
+  void ReconcileElasticOverscrollAndRootScroll() override;
+  void UpdateRootLayerStateForSynchronousInputHandler(
+      const gfx::ScrollOffset& total_scroll_offset,
+      const gfx::ScrollOffset& max_scroll_offset,
+      const gfx::SizeF& scrollable_size,
+      float page_scale_factor,
+      float min_page_scale_factor,
+      float max_page_scale_factor) override;
+  void DeliverInputForBeginFrame() override;
+
+ private:
+  cc::InputHandler* input_handler_;  // Weak. Cleared in WillShutdown().
+
+  DISALLOW_COPY_AND_ASSIGN(UIInputHandler);
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_OVERSCROLL_UI_INPUT_HANLDER_H_